POP: Post Office Protocol

A communications “protocol” is just the language computers use to talk between themselves. POP — the post office protocol — is the language used between a computer fetching email (usually your computer, running an email program) and the computer holding your email (usually that of your email service provider or ISP).

A “POP client” is a program fetching email. Thunderbird and Microsoft Office’s Outlook desktop program are two examples. A “POP server” is the server holding your email.

The “3”in POP3 turns out to be pretty boring. It indicates that we’re all using version three of the POP protocol. It underwent a few revisions before it became what it is today.

IMAP: Internet Message Access Protocol

IMAP is another protocol used by email programs to access your email.

IMAP is an alternative to POP3, and works in a fundamentally different way. Those differences make it a frequently-preferred alternative in today’s always-connected world.

IMAP versus POP3

POP3 is designed around the assumption that when you access your email, you want to download it to the computer you’re using. So after your email program fetches email via POP3, that email resides only on your computer and nowhere else.1 It’s perfect when you only read your email from a single location: your PC.

IMAP assumes you want to leave the master copy of your email on the email server. IMAP is simply a way of looking at that master copy from a connected device. A computer connected via IMAP may (or may not) actually download your email to your computer.2 It’s ideal if you want to access the same email account from several devices.

To configure a POP3 or IMAP account, you generally need three pieces of information:

The name of your email provider’s server which holds your email. Typically, it’s something like “mail.randomisp.com”.

The account ID you were assigned by your ISP. Most commonly it’s your email address, but it doesn’t have to be.

Your password.

That’s it. Once properly configured, you can access the email your ISP collects on your behalf.

SMTP: Simple Mail Transfer Protocol

SMTP is the protocol used to send mail from one computer to another.

When you’re using a desktop email program like Thunderbird, it’s the protocol used when you hit “Send” to transfer your email message from your computer to that of your email provider. What most people don’t realize is that it’s also the protocol used behind the scenes to transfer your message from server to server as it makes its way to the server on which your recipient receives email.

Configuring an SMTP server generally requires the same three things you needed for POP3 or IMAP:

The name of your email provider’s server which will accept your outgoing email. It could be the same as your POP3 or IMAP server, or something different.

The account ID you were assigned by your ISP. Most commonly it’s your email address, but it doesn’t have to be.

Your password.

Webmail works differently, mostly

All of this only applies to email programs you run on your own computer, like Microsoft Office Outlook, Thunderbird, and others.

Web-based email, such as Outlook.com, Yahoo, and the like, displays the email directly from their servers to your web browser. There’s no configuration needed other than logging in. They may use SMTP (and perhaps even IMAP or POP3) behind the scenes to get and send email, but that’s nothing you’d ever need to see, know, or worry about.

The one exception is that many services can be instructed to act like a desktop email program and fetch your email from an email service. For example, say you normally get your mail from randomisp.com, and use Thunderbird to download that email to your PC, using the POP3 protocol. You can, if you like, open a Gmail account and configure this web-based system to fetch your email from randomisp.com, using POP3. That way, instead of reading your email in your desktop email program, you would read it by visiting the Gmail website in your browser.

Footnotes and references

1: Yes, there are options to “leave on server”, but those are, in a sense, hacks added to overcome protocol shortcomings. The primary intent is to keep one master copy of your email in your email program on a single device.

About Leo

Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

The return address is your email address. In most cases it’s the address of the account you’re setting up. If it seems funny they are asking that, it’s because in some cases, people will send from one account and receive it at another.

Thank you very much for the very valuable information about pop vs pop3 and its usage. Also keep up the good work informing people on the tech-integrities of usage on other companies products.
Very valuable indeed!

Okay, I recently got Mozilla Thunderbird, and it is asking for my POP and SMTP, I really don’t understand this. Can you please tell me how this works? Much appreciated, my email is [removed. Never post your email in the body of a comment. -Leo]

I use Mail demon as my mail server and tried to set up a pop account on the same computer. I put in the correct settings but it would not work. When i selected test it would complete the first three options (connect to network, send to server ect) but the last two failed (recieve from server ect). I made sure the port numbers were set at default, disabled my firewall and mail antivirus but it still wouldnt work. I set up the exact same pop account on another computer and it works fine. Any help please?

I use Microsoft Outlook and have an account set up in SMTP. From time to time I want to send pictures or a recipe and when in this picture or recipe I select send and I enter the email of the person I want it to go to, and it goes off to send but I then get a message that it cannot send cause it needs POP3 to send. Am I able to have both SMTP and POP3 at the same time and if so, how do i set this up? Thank you, Sandy

I am trying to set up my Mail account on my Mac. It asks for my email address and password which I’ve filled in. Then the incoming mail server details, i.e. POP, IMAP or Exchange. Then the name of the Incoming Mail server. I don’t know what this is or how I find it. My ISP is Firefox and my normal email account is with MSN [email address removed]

I’m really not computer savvy, and I get tired of trying to send certain e-mails which require this info., which I don’t know. I use yahoo e-mail, what should I put when it asks about http, pop3, whatever….?????

I’m trying to add another account to my Windows Live Messenger and I have everything else but it’s telling me that I need to put in my “POP server”. I don’t even know what that is! How would I find that?

If it’s asking for a POP server, then you’re not configuring Windows Live Messenger. POP is an email thing, and it sounds like you’re somewhere in Windows Live Hotmail instead.

? re my level of competence: I don’t even know what’s meant by using HTML tags for style ;-)and you expect me to really comprehend all the logic and intricacies of pop3, SMTP, IMAP, whatever?;-)) It was six years before I realized I could move ‘Windows’. I’ve used ONLY Yahoo’s web based email program, and whatever I have not deleted I can access on-line. I’d like to insure permenant accessibility to that material and hope I could handle simple directions, if there are any, as opposed to theoretical or technical explanations, to achieve this goal. That there were recent comments was encouraging, even though I’m even dizzier now that I’ve read them ;-)). Would downloading an ‘application’ such as Thunderbird, et al, be the route to go? Is transferring or sharing this material possible somewhere else on line, in the event Yahoo ‘goes down’ for example?. I use two different ISPs and have a few web-based email accounts and run XPsp2, if any of this makes a difference. I am in a panic which may account for why much of the discussion isn’t sticking to the brain. I sure hope you are for real.

I,m trying to use windows mail for my emails I’m with optusnet
windows asks whos my incoming mail pop3server
and whats my outgoing email smtp name
no idea!
must have it half right as it’s picking up my in mail but I can’t send

Somehow I have enabled POP email on my computer. It doesn’y work & I don’t want it. Every outgoing MSN email is not sent unless I change my “from” address to a MSN designation on the dropdown. If I forget to do that, the message is not sent. How do I terminate it?

I am getting that port 110 error how do I fix it on this computer. I have set up my emails on another computer and everything is working alright and then when I go to my own computer it is giving me this error report:The host ‘mail.clients-login.com’ could not be found. Please verify that you have entered the server name correctly. Account: ‘mail.clients-login.com’, Server: ‘mail.clients-login.com’, Protocol: POP3, Port: 110, Secure(SSL): No, Socket Error: 11004, Error Number: 0x800CCC0D. PLEASE HELP URGENTLY

Hi, never had this problem before, but failed to send an email from Outlook Express with the message:
The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was ‘[email removed]@yahoo.com’. Subject ‘Members Only May 1-3 Weekend Sale’, Account: ‘mail.qtiq.com’, Server: ‘mail.qtiq.com’, Protocol: SMTP, Server Response: ‘501 Bad address syntax’, Port: 25, Secure(SSL): No, Server Error: 501, Error Number: 0x800CCC79
Please help!

Everytime I try to send mail in Outlook Express it always says error: either the server name or email address is not correct or server not found make sure you are using the correct server name etc. Help? I don’t know what to do for this problem.

Not to sound to snotty, but consider following the advice in the error message you were given: confirm that your SMTP settings are correct. Check with your ISP or Email provider for what they should be.

I need your help. I have been trying to set my windows Live mail for Windows 7 32 bit. But no result – I cannot open my inbox for these 2 accounts! On Windows Vista they worked properly.
Then I downloaded missing dll drivers and Microsoft Silverlight 5 beta – no result.
Then I tried to set these addresses in Mozilla Thunderbird – but even no connection with server.

Tell me please, what is the problem? What should i do?
I tried very hard but still cannot read my mails, it upsets me((( I have lots of necessary mails connected with my job(

If there will be no good way out – can I transfer my mails to other (not hotmail) accounts?

Some ISP’s are more particular, and may insist upon access via specific port numbers, and/or via SSL, as well as proper username and password, for E-Mail account access.

It scarcely needs saying that these ISP’s are pains in the gazobo!!! 🙁

The process may be painful, but there’s a very important reason ISPs do this: spam. By requiring authentication and using non-standard ports they can deal with spam much more agressively. By connecting correctly it’s extremely unlikely that your email will be blocked by that ISP as spam as you send it out.

It is refreshing to hear someone who answers the questions that a person who asks about computers in a clear and consice manner. I have taken classes in MS office, Word, Excel and I, and many other people, must operate a computer for their jobs. We don’t want to write programs or be an IT person. The computer replaced the pen and pad or the typewriter it is a tool to turn out work product. While it is true the more that you know about them the more effcient you are but I am not enthralled with a computer. After all the classes occasionally I have questions questions that don’t force me to understand how to program the thing. Thanks Leo (suprise, that’s my name too.

@Jan
Your ISP is the company that you get your internet access from such as AT&T, Comcast, Verizon etc.
This article on Ask Leo! – should clear up the confusion of Microsoft’s different Live brands. What is windows live?

@Robert
To turn this feature off, click on “Tools” then “Account settings”. Select “Server settings” for the account you want to change and deselect the checkboxes for “Check for messages at startup” and “Check for messages every xxx minutes”

What do I do with the little box that keeps popping up titled “pop2” with my email and directing me to enter a password in place of the asterisks? No matter what I enter or how many times I delete the box, it comes back. Is something bad going to happen to my computer?

Are you sure that’s a “2”? POP3 is what we expect. Typically that message happens when your email program is trying to download email from an account, and the account server is saying that you have the wrong account name or password configured. The box should include more information about exactly what email account it’s complaining about.

I just bought a Verizon 6 plus, 64 GB! I want to use many of the apps that this phone offers! So, unfortunately this will not be the last time I have a question. I want to do everything correctly! First question is, What password, “that is required” do I enter for POP Account do I enter to begin for neo.rr.com? My home computer is a Dell 8 version ! Sometimes I use Internet Explorer, but I also have a Chrome account set up also!?

That would be the password you use to login to your neo.rr.com account – I’m not sure how else to put it. You should be required to enter a password when you check your email normally – so this would be that password.

I have read at least a dozen articles about, “The Advantages of IMAP”. This article was far and away the very best one I have ever read. If there was a Hall of Fame for computer articles, this would deserve to be in it. Thanks for this wonderful explanation!

First, thank you for your extremely helpful website, and for putting in the time and effort you do.

I have currently have an email address an email I’ve set up via Yahoo’s connection that looks like this (imagine this were its configuration): “admin@firstnamelastname.com. I use that email address ONLY to give others an easy to remember email address (“firstname@firstnamelastname.com”, and have email to that address automatically redirected to my yahoo.com email address. I have never used it as an actual business website for it, even though it offers that service, but solely to redirect all email to it to my actual Yahoo email address assume that were joeblow@yahoo.com).

I recently got an email from Aabaco Small Business (who incidentally I’ve never hear of) titled “Upgrade from POP-only to web &POP”

It goes on to say “Abaco Small Business is discontinuing its POP-only business accounts like this one. Your email account needs to be upgraded within 45 days to prevent loss of access. After the upgrade you’ll still be able to access your email through the same program you do now. After upgrading, you will have these additional options:

WEB — Sign in and check your business email from any web browser, anywhere’
Yahoo Mail App — Manage your business email on the go with our popular app for iOS and Android mobile options

If “Aabaco” is something you’d never heard of my suspicion is that this is nothing more than a phishing attempt. However I would check all the parties involved – your domain registrar, and perhaps more importantly double check whatever technique you’re using to get your mail into Yahoo!. Only scenario I can think of that might be legit is if you’re using Yahoo! to fetch your mail from that domain using POP3, and your registrar is the one providing you with this “AaBaco” service. Certainly Yahoo! isn’t changing what they’re doing right now.

Recently I joined LinkedIn for the purpose of communicating with a classmate (class of ’57). Since then LinkedIn has been sending me emails containing “suggested connections to review” which list people I may know. Many of the names are of people I do know. For example: a classmate from my 6th grade in 1951 who I have not seen since 1951 but have received one email 12 years ago, an acquaintance from whom I have received one email, a cousin of my wife with whom I have never communicated but whose name was listed in an email from a different cousin, and the pastor of a church I attended 5 years go.
The only common denominator between these people and me is email and their being a LinkedIn member. All of them live in cities different than mine. Apparently Google shares information about my email with LinkedIn, including being able to scan the text of the messages for names since I’ve never sent nor received email from the cousin who name was in one message. Also I remove my mail from Google’s server when I download it via POP3.

I don’t believe Linked-in gets email addresses from Google. That would make Google a party to spamming. Linked-in uses their own Email databases built up through addresses they compile through their subscribers.

I can’t really argue. You certainly know more than I. But — It certainly looks suspicious when the names of my acquaintances who live hundreds of miles away and in different cities always appear at the top of their suggestions and yet there is nothing other than a personal email to or from the individual. In the case of the cousin (much different last name) I have never sent nor received an email from him. He was referenced once in an email from a different cousin. All of the 4 people are of vocations different than mine. Too much of a coincidence.

I actually don’t believe Google shares data with LinkedIn (which is owned by Microsoft these days). I think that people provide more than enough information in their LinkedIn profiles for LinkedIn to make the matches. Everyone provides more than enough information for it to start making educated guesses.

The fact that Microsoft owns Linked-in is pretty much proof that Google isn’t sharing that info with them, but Microsoft is at least within an order of magnitude of Google’s data gathering capabilities.

Leo, thank you for your, as always, very helpful article about POP3 and IMAP. When I acquired a smartphone & a Samsung Tablet I thought it would be a good idea to go to IMAP. The result was that I could get the emails from my ISP on the phone & on the tablet, but not on MS Outlook. Asked my ISP for help, they set it all back to POP on the computer, they said that IMAP is not working. I wonder if it has anything to do with the ISP’s call center is in the Philippines? Now I have to delete unwanted emails on 3 devices!

Linda, I too have a very similar problem. In the family we have Two tablets and Two phones and a “family” e-mail all are “set” to use IMAP (I think). Sometimes an e-mail deleted from any one of them seems to be deleted on them all . . . and sometimes, like you I have to delete the same message from each one individually. Odd Eh?

it could be that I am using a mix of “programmes Samsung mail (very user friendly) and Google mail (for Samsung)

Free Newsletter!

Subscribe to The Ask Leo! Newsletter and get a copy of The Ask Leo! Guide to Staying Safe on the Internet – FREE Edition. This ebook will help you identify the most important steps you can take to keep your computer, and yourself, safe as you navigate today’s digital landscape.

Then each week in The Ask Leo! Newsletter you’ll get even more tips, tricks, answers and ideas to help you use your technology more effectively and stay safe doing so.